Change calendar language to English
Go to System Settings, then to Language Support. From there open the second tab which is named "Regional Formats". Then change the drop down bar's content from "Arabic" to the English language variant you like and you're all set.
Re-login for this to take effect
Go to Settings > Region & Languages > Formats; click on the formats and change it from your default country to either UnitedStates or UnitedKingdom and then re-log in.. that should do